(A) study on the three-dimensional upset forging of prismatic blocks

Abstract

The prediction of metal flow together with forging load in upset forging is very important, since it makes a great influence on the deformed shapes, mechanical properties and surface defects. The present study is concerned with upset forging of non-circular prismatic blocks in which the developed metal flow is nonuniform both in the plane section of the billet and along its thickness. Upset forging of non-circular blocks is characterized by the three-dimensional deformation with lateral sidewise spread as well as axial bulging along thickness occurring in the plane including the upsetting axis. For the analysis of upset forging of general prismatic blocks a kinematically admissible velocity field to incorporate the three-dimensional deformation is proposed. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. In computation the deforming region is divided into the finite number of small elements and the work-hardening effect is considered for each elemental region. The analysis is made in three stages according to the billet shape. i) Upset forging of elliptical disks of various aspect ratios. ii) Upset forging of regular polygonal blocks; as examples, regular triangle, square and regular hexagon. iii) Upset forging of arbitrarily-shaped prismatic blocks; as examples, clover and rounded rectangles of various aspect ratios. In order to confirm the validity of the proposed velocity field, experiments have been carried out with annealed AISI 1015 steel billets and commercially pure copper billets at room temperature for different geometrical shape and frictional conditions. The theoretical predictions both in the forging load and the deformed configuration are shown to be in good agreement with the experimental results. Therefore, the proposed method of analysis in the present study can be used for the prediction of forging load and defo...